If you want to cycle get a hat.

 I went with my daughter to buy he son a cycle helmet. These didn't exist as far as I know when I was young.

When we were ten years old, some friends and I cycled about forty miles to the nearest city and camped there overnight before cycling back the following day. Yes there were fewer cars on the roads but none of us wore helmets.

More innocent times.

Swimming

 Does anyone swim regularly? Obviously it helps if you live close to a swimming pool but it is great exercise which works all the muscles with no impact.And it is a true year round activity.